The invention relates to a method for reducing jerking during gear shifting of an automatic transmission driven by an internal combustion engine.
As disclosed in "Funktionsbeschreibung Automatikgetriebe, 5 HP 19 FL" of ZF Getriebe GmbH Saarbrucken, issued in August 1995, an automatic transmission with a selector lever having a forward drive (D) and reverse drive (R) positions, and parking (P) and neutral (N) positions. In the R, N and D positions (first gear) a first clutch is closed. By moving from position D to N a second clutch is opened and by moving from the position R to N a third clutch is opened. In an automatic transmission of this kind a problem can arise in the practice: when gear shifting, that is, in the transition from the position D to N or from R to N, respectively the second or third clutch is opened. The shifting quality when changing gears is determined by the manner in which it is possible to smoothly carry out the torque reduction. Decisive for this are, on one hand, design of the vehicle and, on the other, the duration of pressure reduction of the clutch being disengaged. However, the requirement of a good shifting quality is opposed to the requirement of adequate safety and durability criteria. These determine that under all conditions, such as low temperatures, the clutch to be disengaged must be drained with certainty. If this is not ensured, then when the clutch opens and the accelerator pedal is simultaneously actuated, there can result a destruction of the clutch. Since the safety and durability criteria must be ranked above the comfort demands, jolts occurring when gear shifting have hitherto been accepted.
The problem on which the invention is based is now to provide for the above described automatic transmission that both requirements, namely, comfort and safety, be satisfied.